Today's ultra-low power integrated circuits are able to operate with currents of less than 1 micro Ampere (μA). In order to achieve the required stable supply voltages, the supply voltage is compared with a reference voltage. Such an integrated circuit usually has several voltage domains. Each voltage domain has its individual supply voltage. Each supply voltage must be compared with several pre-selected reference voltages. An individual comparator per each voltage is used to determine whether or not supply voltages are above or below pre-selected reference voltages. Each comparator can only consume a fraction of the 1 μA current used for the whole electronic device. The remainder of the power must be preserved for several other components of the electronic device. Therefore, it is desirable to compare supply voltages of different voltage domains with multiple pre-selected reference voltages while consuming only a small amount of power.